1. Field of the Invention
This invention relates to stretchable interconnects employing stress gradient films. The stretchable interconnects are particularly suitable for flexibly connecting movable sensors in arrays such as the tactile sensitive skins of robots.
2. Prior Art
Photolithographically patterned spring contacts having a stress gradient formed therein which causes the spring contact to bend away from a substrate to provide an interconnect have been described in U.S. Pat. Nos.: 5,613,861 to Smith et al., U.S. Pat. No. 5,848,685 to Smith et al., U.S. Pat. No. 5,914,218 to Smith et al., U.S. Pat. No. 5,944,537 to Smith et al. and U.S. Pat. No. 5,979,892 to Smith. U.S. Patent Applications Nos.: 09/573,815 for xe2x80x9cPhotolithographically Patterned Out-Of-Plane Coil Structures And Method Of Makingxe2x80x9d, to Chua et al. and 09/572,200 for xe2x80x9cMethod of controlling stress anisotropy in thin film structuresxe2x80x9d to inventor David Fork also relate to photolithographically patterned spring contacts. These patents and patent applications are specifically incorporated by reference herein in their entirety.
In robotic design it would be useful to have surface coatings or skins embedded with sensors and control hardware. Such a skin needs to be flexible and stretchable to conform to tactile movement or to movable appendages. Providing stretchable interconnects which can withstand such deformation is a major challenge.
A variety of tactile sensing skins have been employed in robots in an effort to sense applied force levels, torque levels, etc. and the position of the work piece which is being acted upon by the robot. U.S. Pat. Nos.: 4,588,348 to Beni et al., U.S. Pat. No. 4,694,231 to Alvite, and U.S. Pat. No. 4,817,440 to Curtin are illustrative of robots employing such tactile sensing skins. These patents are specifically incorporated by reference herein in their entirety.
In accordance with this invention there is provided a stretchable interconnect for electrically connecting electronic devices which are supported for movement relative to one another. The interconnect comprises a photolithographically patterned stretchable conductor extending between two of the electronic devices for electrically coupling a contact of one device to a contact of another device. Preferably the interconnect comprises a coiled conductor. The coiled conductor is comprised of a conductive material having a stress gradient extending through at least a portion of the thickness of the conductor.
In a preferred embodiment the stretchable interconnect is photolithographically patterned and comprises at least one xe2x80x9cVxe2x80x9d shaped section, which, when unsupported, forms the stretchable interconnect which is preferably a coil. Most preferably the interconnect comprises a plurality of xe2x80x9cVxe2x80x9d shaped sections, which, when unsupported forms the stretchable interconnect, which is preferably a coil. Preferably the coiled conductor of the stretchable interconnect is di-helic, and is made up of segments having right-handed and left-handed helical windings.
In accordance with yet another embodiment of the invention a sensor array is provided which comprises at least two electronic devices which are supported for movement relative to one another and at least one stretchable interconnect for connecting the electronic devices. As in the previous embodiment the interconnect comprises: a photolithographically patterned conductor extending between the devices for electrically coupling a contact of one device to a contact of another device. The conductor is preferably a coil which is formed of a conductive material and has a stress gradient extending through a thickness of the conductor. The interconnect as photolithographically patterned preferably comprises at least one xe2x80x9cVxe2x80x9d shaped section, which when unsupported, forms a stretchable interconnect which preferably is in the form of a coil. Most preferably it comprises a plurality of xe2x80x9cVxe2x80x9d shaped sections, which when unsupported form the stretchable interconnect. The coil form of the interconnect is most preferably di-helic.
The sensor array preferably comprises a tactile sensing array. In a particularly preferred embodiment the sensing array comprises a tactile sensing portion of a robot. The sensor array in accordance with the preferred embodiment is arranged in a flexible and stretchable skin of the robot. The sensor array preferably includes a plurality of the stretchable interconnects.
In accordance with yet another preferred embodiment of the invention a process is provided for making a stretchable interconnect for electrically connecting electronic devices which are supported for movement relative to one another. The process comprises forming the devices supported by a substrate, the devices being spaced apart from each other as supported by the substrate. An interconnect conductor is deposited which is supported by the substrate for electrically coupling a contact of one electronic device to a contact of another electronic device. The interconnect conductor is preferably formed with a stress gradient extending through at least a portion of the thickness of the conductor. The interconnect conductor is photolithographically patterned with a pattern which upon removal of the substrate from support of the interconnect conductor will cause the interconnect conductor to form a stretchable interconnect which is preferably in the form of a coil.
In a preferred embodiment of the process the interconnect conductor as photolithographically patterned and prior to substrate removal comprises at least one xe2x80x9cVxe2x80x9d shaped section, which when unsupported forms the stretchable interconnect which is preferably in the form of a coil. In an even more preferred embodiment the photolithographically patterned interconnect conductor comprises a plurality of xe2x80x9cVxe2x80x9d shaped sections, which when unsupported form the stretchable interconnect which is preferably in the form of a coil. Most preferably the interconnect conductor when unsupported is a di-helic coil.
In a further embodiment of the invention the process further includes forming a sensor array having more than two electronic devices and including a plurality of stretchable interconnect conductors connecting adjacent electronic devices. The process preferably further comprises mounting the sensor array to a flexible and stretchable skin material. The sensor array preferably comprises a tactile sensing array which most preferably comprises a tactile sensing portion of a robot.
This invention is aimed at providing an improved stretchable interconnect for electrically connecting electronic devices which are supported for movement relative to one another. It is also aimed at providing an improved sensor array employing such stretchable interconnects. It is also aimed at providing an improved process for forming such stretchable interconnects and sensor arrays.